linux进程 生产者消费者

Posted 2020-12-24 子都

#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<fcntl.h>
int lock_set(int fd,int type)
{
	struct flock lock;
	lock.l_whence= SEEK_SET;
	lock.l_start = 0;
	lock.l_len = 0;
	lock.l_type = type;
	lock.l_pid = -1;
	fcntl(fd,F_GETLK,&lock);
	if(lock.l_type != F_UNLCK)
	{
		if(lock.l_type == F_RDLCK)
		{
			printf("Read lock alread set by %d
",lock.l_pid);
		}
		else if(lock.l_type == F_WRLCK)
		{
			printf("Write lock alread set by %d
",lock.l_pid);
		}
	}
	lock.l_type = type;
	if((fcntl(fd,F_SETLKW,&lock)) < 0)
	{
		printf("Lock failed:type = %d
",lock.l_type);
		return -1;
	}
	switch(lock.l_type)
	{
		case F_RDLCK:
			{
				printf("Read lock set by %d
",getpid());
			}
			break;
		case F_WRLCK:
			{
				printf("Write lock set by %d
",getpid());
			}
			break;
		case F_UNLCK:
			{
				printf("Release lock by %d
",getpid());
			}
			break;
	}
	return 0;
}
int custum()
{
	int fs,fd;
	int count;
	char c;
	if((fs = open("produce.txt",O_RDWR)) < 0)
	{
		printf("open error
");
		return -1;
	}
//	if((fd = open("temp.txt",O_RDWR)) < 0)
//	{
//		printf("open error2
");
//		return -1;
//	}
	while(1)
	{
		lock_set(fs,F_WRLCK);
		lseek(fs,0,SEEK_SET);
		fd=open("temp.txt",O_RDWR|O_CREAT|O_TRUNC,0777);
		count=read(fs,&c,1);
		if(count <= 0)
		{
			printf("no product!
");
			lock_set(fs,F_UNLCK);
			sleep(1);
			continue;
		}
		printf("get a character: %c 
",c);
	//	lseek(fs,0,SEEK_CUR);
	//	lseek(fd,0,SEEK_SET);
	//	count = 0;
		while(((count = read(fs,&c,1)) == 1) /*&& c!= ‘
‘*/)
		{
			printf("read fs: %c
", c);
			write(fd,&c,count);
		}
		close(fs);
		fs = open("produce.txt",O_RDWR|O_TRUNC);
		//[email protected]
		lseek(fs,0,SEEK_SET);
		lseek(fd,0,SEEK_SET);
		while(((count = read(fd,&c,1)) == 1) /*&& c!=‘
‘*/)
		{
		//	printf("read fd: %c
", c);
			write(fs,&c,count);
		}
		unlink("temp.txt");
		close(fd);
		lock_set(fs,F_UNLCK);
		sleep(2);
	}
}

int main(int argc, const char *argv[])
{
	custum();


	return 0;
}

　　运行程序时，生产文件里有ABC 3个产品，运行时发现最后一个C产品一直会重复取出，经检查发现：我将produce.txt中的剩余产品复制到temp.txt中，之后再复制回来，我只是将文件读写位置调到了起始，但是以读写方式打开文件produce.txt，其中的产品仍为ABC，将temp.txt中的BC复制回去时，只是覆盖AB为BC最后的C仍存在，所以会一直有C。解决这个问题是：关闭produce.txt的文件符，重新以读写，清除原文件内容的方式打开，就会成功。只是还有一个问题read函数读到最后貌似自动会读一个‘ ‘。不加语句c!=‘ ‘的话，会将 一直复制下去。

生产者函数如下：

#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<fcntl.h>
int lock_set(int fd,int type)
{
	struct flock lock;
	lock.l_whence = SEEK_SET;
	lock.l_start = 0;
	lock.l_len = 0;
	lock.l_type = type;
	lock.l_pid = -1;
	fcntl(fd,F_GETLK,&lock);
	if(lock.l_type != F_UNLCK)
	{
		if(lock.l_type == F_RDLCK)
		{
			printf("Read lock alread set by %d
",lock.l_pid);
		}
		else if(lock.l_type == F_WRLCK)
		{
			printf("Write lock alread set by %d
",lock.l_pid);
		}
	}
	lock.l_type = type;
	if((fcntl(fd,F_SETLKW,&lock)) < 0)
	{
		printf("Lock failed:type = %d
",lock.l_type);
		return -1;
	}
	switch(lock.l_type)
	{
		case F_RDLCK:
			{
				printf("Read lock set by %d
",getpid());
			}
			break;
		case F_WRLCK:
			{
				printf("Write lock set by %d
",getpid());
			}
			break;
		case F_UNLCK:
			{
				printf("Release lock by %d
",getpid());
			}
			break;
	}
	return 0;
}
int produce()
{
	int fd;
	char a=‘A‘;
	if((fd = open("produce.txt",O_WRONLY|O_APPEND)) < 0)
	{
		printf("open failed
");
		return -1;
	}
	while(1)
	{
		lock_set(fd,F_WRLCK);
		write(fd,&a,1);
		printf("hava produce one character %c 
",a);
		a++;
		lock_set(fd,F_UNLCK);
		sleep(3);
	}
	close(fd);
}
int main(int argc, const char *argv[])
{
	
	produce();
	return 0;
}